When drilling a well bore which penetrates one or more subterranean earth formations, it is sometime advantageous or necessary to create a hardened plug in the well bore. Such plugs can be used for abandonment of the well, isolation of particular zones of the well bore, enhancement of well bore stability, to place a whipstock or sidetrack for creation of a new well bore which deviates from the original well bore, or kick-off procedures.
Typically, a cement or polymer-based plug can be set in a well bore by pumping a volume of spacer fluid compatible with drilling mud and cement slurry into the work string. Then a pre-determined volume of a cement or polymer containing slurry is pumped behind the spacer fluid. The slurry travels down the work string and exits through one or more openings located at the end of the work string. In this context, the end of the work string is usually referred to as the “tail pipe.” Drilling fluid is usually pumped behind the slurry to maintain pressure within the work string.
At this point, the work string is raised within the well bore to permit the entire volume of slurry inside the conduit to flow out of the bottom of the tail pipe. However, the tail pipe must be raised very slowly or the slurry and the drilling fluid will mix, which may destroy the integrity of the plug. The process of raising the tail pipe generally causes damage to the plug because, as the tail pipe is raised, the drilling fluid in the work string mixes with the slurry.
It should be understood that the various aspects are not limited to the arrangements and instrumentality shown in the drawings.